Pliers typically comprise two legs rotatably connected to each other via a pivot and forming a working section and a handle section which are separated from each other in the area of the pivot. Each leg comprises an inner side, said inner side facing the inner side of the other leg, an outer side opposite said inner side, a front side and a rear side.
The application of fine mechanical or medical pliers typically requires a precisely controlled dosage and transmission of force, and the specific positioning of the working side at or in a working area. Said working area may be any material or a body portion of a patient, e.g. in the head or in an organ, having strictly limited space conditions. These activities may be required in normally accessible working areas or in hardly accessible apertures. During operation, the forces used may change from mere holding and positioning to the transmission of greater forces, such as e.g. for pinching operations.
The dynamic application of these pliers requires exact guiding capability. At the same time it should be possible that the position of the handle of the pliers can be easily changed in the hand during operation. Furthermore, it should be possible that the pliers can be easily and rapidly opened and closed in a precisely controllable manner.
During these activities, the pliers are usually opened by contacting the inner side of one leg of the handle with the small finger and/or also additionally with the ring finger, while they are closed with the remaining fingers contacting the outer side of the leg of the handle. In prior art pliers, there is no specific contacting or engagement area for the thumb during these opening and closing operations.
DE-A-35 45 411 and EP-A-0 228 032 disclose multi-purpose pliers whose legs of the handle form one jaw each at their ends and are in working connection via a hinge. The legs of the handle of these pliers oppose each other in an ellipse-like manner in the plane of the legs of the handle. In the region of the coupling area with the hand, the legs of the handle have an ellipse-like cross-section. At each of the lateral flanks of the legs of the handle, there is a waisted recess provided in the region of the rest for the index finger and thumb. These recesses serve as bed for the thumb on the front side of the leg and as bed for the index finger on the rear side of the leg. These pliers in particular have the drawback that they do not sufficiently match the anatomy and anthropometry of the human hand, which is the reason why, in use, there are rapidly signs of tiredness and the pliers can no longer be positioned sufficiently precisely. On account of the ellipse-like design of the legs of the handle of the pliers, there is the further disadvantage that they can be applied in narrowly restricted working spaces to a limited extent only. The design of the thumb and index finger rest does not correspond to the optimum ergonomic aspects either and is therefore only insufficiently appropriate for continuous precise handling as is necessary for the purpose of fine mechanical and medical tasks.
DE-U-93 20 922 discloses an ergonomic handle structure for tools. The two legs of the handle of these pliers have an arch-like shape, wherein the radius of the arch and the curvature may vary. For achieving an ergonomic handle design, it is suggested that the arched handle parts are extended by the use of extension pieces which are made of a flexible plastics material. These pliers are disadvantageous in that the flexible extensions of the legs of their handle do not permit precise handling when holding the pliers at their rear ends. Further drawbacks consist in that, while the flexible leg ends can match the hand of a user, it always requires force or pressure to adjust the shape of the handle. This entails tender spots and undesired tenseness in the user, which considerably restricts the handleability of the pliers, in particular in the field of fine mechanics or medicine. With the design of the pliers with extensions at the legs of the handle, said pliers are useful for the application in narrowly restricted spaces to a limited extent only.
DE-U-71 02 040 relates to a knife haft comprising grooves having various lengths and intended to permit firm gripping of the knife haft. The sides of the knife haft may be provided with a very rough surface. The knife haft is preferably provided with an oval recess at its upper side for receiving the thumb.
DE-U-91 12 630 relates to a handle for tools which consists of an elongate handle sleeve which is made of plastics. The handle sleeve is to be placed on a leg of pliers and comprises an inner surface and an outer gripping surface. The handle sleeve is formed of a compression-elastically deformable soft plastics material at least in the region of the gripping area.
DE-C-41 17 899 relates to pliers comprising a hinge, a tool end and a handle end, wherein each end comprises two legs and each leg exhibits one inner surface, one outer surface and two lateral surfaces. When a finger presses against the inner surface of a handle leg during opening the pliers with one hand, a supporting section at said inner surface prevents the finger from slipping.
All of these known pliers have the disadvantage of poor handleability, in particular because ergonomic aspects as well as the motions actually taking place when handling pliers have insufficiently been taken into consideration.